Noise eliminating device and program therefor

ABSTRACT

To obtain a noise eliminating device which is capable of efficiently separating a noise component from an image component to attenuate only the noise component. A noise eliminating device includes: a first input reading unit ( 101 ) for reading out input image block data of a predetermined block; a second input reading unit ( 102 ) for reading out reference data containing data in the vicinities of the predetermined block; an output reading unit ( 104 ) for reading out output image block data of the predetermined block; a comparing unit ( 105 ) for comparing a level of a difference signal representing a difference between the input image block data and the output image block data with a predetermined value; a retrieving unit ( 106 ) for retrieving retrieval block data correlating with the input image block data; a switching unit ( 107 ) for outputting output image block update data based on comparison results; an output writing unit ( 111 ) for writing the scaled output image block update data to an output image buffer ( 103 ); and a control unit ( 112 ) for successively carrying out setting of a plurality of predetermined blocks.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a noise eliminating device for reducinga noise contained in an image signal such as a video signal, and to aprogram for the noise eliminating device.

2. Description of the Related Art

There exist many devices and methods for eliminating a noise from animage signal. For example, a technique is known in which a differencebetween a signal obtained from a certain pixel and a signal obtainedfrom a pixel orthogonally adjacent to the certain pixel is obtained, anda value obtained by multiplying the difference by k is subtracted fromthe signal obtained from the certain pixel (see JP 07-184225 A, page 1,FIG. 1). According to this method, when a small difference is obtained,a probability that each of the two signals is a noise component is high,and hence a value of k is increased, while a large difference isobtained, a probability that each of the two signals is an imagecomponent is high, and hence a value of k is decreased.

In addition, a technique is known in which a plurality of noiseeliminating filters, and means for detecting a horizontal edge and avertical edge of an image signal are provided, and horizontal smoothingand vertical smoothing are carried out based on the detected horizontaledge and the detected vertical edge, respectively, thereby reducing anoise contained in an image signal (see JP 09-200579 A, page 1, FIG. 1).

However, the conventional technique involves the following problem. Theconventional noise eliminating method depends on a local property of animage. Thus, the noise is reduced by filters having differentcharacteristics. However, since the accuracy of detecting the localproperty is poor, the noise component is imperfectly separated from theimage component due to failure in judgment or mismatching between thejudgment result and the characteristics of the filters in some cases. Asa result, there is encountered a problem in that the noise eliminationcauses new disturbance, and so forth.

SUMMARY OF THE INVENTION

The present invention has been made in order to solve the problem asdescribed above, and it is, therefore, an object of the presentinvention to obtain a noise eliminating device capable of efficientlyseparating a noise component from an image component to attenuate onlythe noise component.

According to the present invention, there is provided a noiseeliminating device for eliminating a noise contained in an input imagesignal to generate an output image signal, including: an input imagebuffer for storing the input image signal; an output image buffer forstoring the output image signal; an intermediate image buffer forstoring an intermediate image signal for which a noise eliminatingprocessing is being executed; a first input reading means for readingout an image signal of a predetermined block specified by apredetermined position and a predetermined size as input image blockdata from the input image buffer; a second input reading means forreading out image signals containing the image signals of thepredetermined block and vicinities of the predetermined block asreference data from the input image buffer; output reading means forreading out an image signal of the predetermined block as output imageblock data from the output image buffer; comparing means for comparing adifference signal representing a difference between the input image datablock and the output image block data with a predetermined value;retrieving means for retrieving block data correlating with the inputimage block data as retrieval block data from the reference data;switching means for receiving as its inputs the output image block dataand the retrieval block data to select the output image block data asoutput image block update data when a level of the difference signal isequal to or smaller than the predetermined value based on comparisonresults obtained by the comparing means and to select the retrievalblock data as output image block update data when the level of thedifference signal is larger than the predetermined value based on thecomparison results obtained by the comparing means; intermediate writingmeans for writing, to the intermediate image buffer, the output imageblock update data selected by the switching means as the intermediateimage signal for which the noise eliminating processing is beingexecuted; multiplying means for scaling the output image block updatedata accumulated in the intermediate image buffer; output writing meansfor writing the output image block update data scaled by the multiplyingmeans to the output image buffer; and control means for carrying outoverall control to successively set a plurality of predetermined blockseach having a predetermined size for a plurality of predeterminedpositions, and to update output image data accumulated in the outputimage buffer with a plurality of output image block update datarespectively corresponding to the plurality of predetermined blocks.

According to the present invention, there is provided a program for anoise eliminating device that eliminates a noise contained in an inputimage signal to generate an output image signal, in which the programcauses a computer to execute: a first input reading means for readingout an image signal of a predetermined block specified by apredetermined position and a predetermined size as input image blockdata from an input image buffer for storing the input image signal; asecond input reading means for reading out image signals containing theimage signals of the predetermined block and vicinities of thepredetermined block as reference data from the input image buffer;output reading means for reading out an image signal of thepredetermined block as output image block data from an output imagebuffer for storing the output image signal; comparing means forcomparing a difference signal representing a difference between theinput image data block and the output image block data with apredetermined value; retrieving means for retrieving block datacorrelating with the input image block data as retrieval block data fromthe reference data; switching means for receiving as its inputs theoutput image block data and the retrieval block data to select theoutput image block data as output image block update data when a levelof the difference signal is equal to or smaller than the predeterminedvalue based on comparison results obtained by the comparing means and toselect the retrieval block data as output image block update data whenthe level of the difference signal is larger than the predeterminedvalue based on the comparison results obtained by the comparing means;intermediate writing means for writing, to the intermediate imagebuffer, the output image block update data selected by the switchingmeans as an intermediate image signal for which a noise eliminatingprocessing is being executed; multiplying means for scaling the outputimage block update data accumulated in the intermediate image buffer;output writing means for writing the output image block update datascaled by the multiplying means to the output image buffer; and controlmeans for carrying out overall control to successively set a pluralityof predetermined blocks each having a predetermined size for a pluralityof predetermined positions, and to update output image data accumulatedin the output image buffer with a plurality of output image block updatedata respectively corresponding to the plurality of predeterminedblocks.

According to the present invention, it is possible to obtain the noiseeliminating device capable of detecting local correlations of an imagefrom multiple directions to eliminate a noise component by utilizing thedirection having the highest correlation to efficiently separate thenoise component from the image component, thereby attenuating only thenoise component, and the program for the noise eliminating device.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a block diagram showing a configuration of a noise eliminatingdevice according to Embodiment 1 of the present invention;

FIG. 2 shows a code describing an operation of the noise eliminatingdevice according to Embodiment 1 of the present invention;

FIG. 3 is a conceptual diagram showing a retrieval range retrieved byretrieving means of the noise eliminating device according to Embodiment1 of the present invention; and

FIGS. 4A to 4D are respectively diagrams showing block positions when aphase in Embodiment 1 of the present invention is changed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of a noise eliminating device and aprogram for the noise eliminating device of the present invention willbe described with reference to the accompanying drawings. A feature ofthe noise eliminating device and the program for the noise eliminatingdevice of the present invention is that a processing for replacing onlydata in which distortion (a difference between an input image signal andan output image signal) is large with adjacent data is repeatedlyexecuted while a block size is gradually reduced, thereby eliminating anoise without involving large distortion.

Embodiment 1

FIG. 1 is a block diagram showing a configuration of a noise eliminatingdevice according to Embodiment 1 of the present invention. In FIG. 1, aninput image buffer 100 is a buffer for accumulating input image signals.A first input reading means 101 is connected to the input image buffer100 in order to read out an image signal of a predetermined blockspecified by a predetermined position and a predetermined size as inputimage block data.

A second input reading means 102 is connected to the input image buffer100 in order to read out input image data of the predetermined block theimage signal of which is read out by the first input reading means 101and input image data in the vicinities of the predetermined block asreference data.

An output image buffer 103 is a buffer for preserving an output imagesignal. An output reading means 104 is connected to the output imagebuffer 103 in order to read out an image signal of the predeterminedblock the image signal of which is read out by the first input readingmeans 101 as output image block data. A comparing means 105 receives asits inputs the input image block data of the predetermined block readout by the first reading means 101 and the output image block data ofthe above predetermined block read out by the output reading means 104to compare a difference between the input image block data and theoutput image block data with a predetermined value D.

A retrieving means 106 retrieves data most approximating the input imageblock data read out by the first input reading means 101 (i.e., the datahaving the highest correlation) from the reference data read out by thesecond input reading means 102 as retrieval block data. A switchingmeans 107 selects either the output image bock data as an output of theoutput reading means 104 or the retrieval block data as an output of theretrieving means 106 based on comparison results obtained by thecomparing means 105 and outputs the selected data as output image blockupdate data.

An intermediate writing means 108 is means for writing the output imageblock update data selected by the switching means 107 as an intermediateimage signal for which a noise eliminating processing is being executed.An intermediate image buffer 109 is a buffer for accumulating the outputimage block update data written by the intermediate writing means 108.

A multiplying means 110 is means for carrying out scaling by multiplyingthe output image block update data accumulated in the intermediate imagebuffer 109 by a predetermined value. An output writing means 111 writesthe output image block update data scaled by the multiplying means 110to the output image buffer 103, thereby updating the output image.

Moreover, a control means 112 is connected to the reading means such asthe first input reading means 101, the second input reading means 102,and the output reading means 104, and the writing means such as theintermediate writing means 108 and the output writing means 111 in orderto make overall control on determination of a predetermined position anda predetermined size which are used to regulate a predetermined block,or a timing for an arithmetic operation processing.

Next, an operation of the noise eliminating device shown in FIG. 1 willbe described with reference to a pseudo code corresponding to a programfor carrying out noise elimination. FIG. 2 shows a code describing theoperation of the noise eliminating device according to Embodiment 1 ofthe present invention. In FIG. 2, reference symbol V corresponds to theoutput image data accumulated in the output image buffer 103, andreference symbol C corresponds to the intermediate image dataaccumulated in the intermediate image buffer 109. In addition, referencesymbol N designates a size of a block, reference symbol K designates thenumber of overlapped blocks (i.e., corresponds to the number of phaseswhich will be described later), and reference symbol L designates thenumber of blocks.

In addition, a suffix j represents a kind of certain phase of phases 1to K, and a suffix i represents a predetermined block of blocks 1 to L.Also, reference symbol Vi^(NΦ(j)) designates output image block datacorresponding to a phase j and a block i and has elements for N×Npixels. Reference symbol Bi^(NΦ(j)) designates input image block datacorresponding to the phase j and the block i and has the elements forN×N pixels. Moreover, reference symbol Ri^(NΦ(j)) designates retrievalblock data corresponding to the phase j and the block i and has theelements of N×N pixels.

Firstly, the input image buffer 100 stores an input image signal, and avalue V of the output image buffer 103 is initialized to zero (firstline in FIG. 2). Next, the first input reading means 101 and the outputreading means 104 successively read out the image block datacorresponding to the phase j and the predetermined block i from theinput image buffer 100 and the output image buffer 103, respectively. Asize of this block is assumed to be N (pixels)×N (pixels). However, theshape of the block is not limited to a square.

Here, an initial value of N is assumed to be Nmax (first line in FIG.2). In a case where the input image is of a VGA size (640×480 pixels) orso, a typical value of Nmax is in a range of 32 to 64. After N isinitialized, a value C of the intermediate image buffer 109 isinitialized to zero (third line in FIG. 2).

Next, the input image block data Bi^(NΦ(j)), as the output of the firstinput reading means 101, corresponding to the phase j and the block i,and the output image block data Vi^(NΦ(j)), as the output of the outputreading means 104, corresponding to the phase j and the block i areinputted to the comparing means 105. The comparing means 105 compares alevel of a signal representing a difference between the input imageblock data Bi^(NΦ(j)) and the output image block data Vi^(NΦ(j)) with apredetermined value D (sixth line in FIG. 2).

Here, the level of the difference signal, for example, can be calculatedas a value which is obtained by dividing a total sum of absolute valuesof the difference signals for the pixels corresponding to the two imageblock data, i.e., Bi^(NΦ(j)) and Vi^(NΦ(j)), or a total sum of electricpowers each obtained as a square of the difference signal by the numberof pixels, N×N.

When the level of the difference signal is represented by d, if thecomparison results show a relationship of d>D, the comparing means 105sets the input signal to the switching means 107 to the retrieval blockdata Ri^(NΦ(j)) as the output of the retrieving means 106. On the otherhand, if the comparison results show a relationship of d≦D, thecomparing means 105 sets the input signal to the switching means 107 tothe output image block data Vi^(NΦ(j)) as the output of the outputreading means 104.

Thus, when the level d of the difference signal is smaller than thepredetermined value D, the switching means 107 outputs the output imageblock data Vi^(NΦ(j)) as the output of the output reading means 104 asit is. On the other hand, when the level d of the difference signal isequal to or larger than the predetermined value D, the switching means107 outputs the retrieval block data Ri^(NΦ(j)) as the output of theretrieving means 106 instead of the output block data Vi^(NΦ(j)) andtransfers the retrieval block data Ri^(NΦ(j)) to the intermediatewriting means 108 (seventh and eighth lines in FIG. 2).

Here, a description will be given with respect to the retrieval blockdata Ri^(NΦ(j)) as the output from the retrieving means 106. The firstinput reading means 101 reads out the input image block data Bi^(NΦ(j))corresponding to the phase j and the block i from the input image buffer100. Also, the second input reading means 102 reads out the input imageblock data Bi^(NΦ(j)) and its peripheral data from the input imagebuffer 100.

The data which has been read out by the second input reading means 102is supplied as the reference data to the retrieving means 106. Theretrieval means 106 retrieves the data most approximating the inputimage data block Bi^(NΦ(j)) supplied from the first input reading means101 (i.e. the data having the highest correlation) from the referencedata supplied from the second input reading means 102, and outputs theretrieval results as the retrieval block data Ri^(NΦ(j)) to theswitching means 107.

Here, similarly to the case of the above-mentioned comparing means 105,the retrieving means 106 can use a value which is obtained by dividing atotal sum of absolute values of the difference signals or a total sum ofelectric powers each obtained as a square of the difference signal bythe number of pixels, N×N, as a measure of the correlation. Theretrieving means 106 extracts data with the smallest value as theretrieval block data Ri^(NΦ(j)).

In addition, the retrieval processing by the retrieving means 106 isexecuted except for the data in the position corresponding to that ofthe input image block data read out by the first input reading means101, and for the data in the vicinities of the position. Unless thismeasure is carried out, the retrieving means 106 usually outputs its ownblock data (the input image block data itself read out by the firstinput reading means 101) as the retrieval block data Ri^(NΦ(j)). As aresult, the noise eliminating device shown in FIG. 1 cannot perform thefunction of eliminating a noise.

FIG. 3 is a conceptual diagram showing a retrieval range retrieved bythe retrieving means 106 of the noise eliminating device according toEmbodiment 1 of the present invention. There is shown the retrievalrange when the retrieval processing is executed except for an areawithin a distance (radius) equal to or shorter than a size of one pixelfrom a predetermined block as a center. Also, in FIG. 3, when a size ofone predetermined block is assumed to be 8×8 pixels, directions anddistances for the retrieval for a pixel located in upper left of theblock of 8×8 pixels are indicated by arrows.

This process is also applied to each of other pixels within the block.Thus, the retrieval is carried out in blocks for all the pixels usingthe same vectors. That is, in an example shown in FIG. 3, a valueobtained by dividing a total sum of absolute values of the differencesignals, or a total sum of electric powers each obtained as a square ofthe difference signal by the number of pixels, N×N, is obtained for 8×8pixels, i.e., 64 pixels in total for 16 patterns indicated by respectivearrows. Then, the smallest value among those values is selected as thedata most correlating with the input image block data to obtain theretrieval block data Ri^(NΦ(j)).

As previously described, the switching means 107 switches between theoutput image block data Vi^(NΦ(j)) as the output of the output readingmeans 104 and the retrieval block data Ri^(NΦ(j)) as the output of theretrieving means 106 based on the comparison results obtained by thecomparing means 105 and transfers the output image block data Vi^(NΦ(j))or the retrieval block data Ri^(NΦ(j)) as the output image block updatedata to the intermediate writing means 108.

The intermediate writing means 108 writes, to the intermediate imagebuffer 109, the output image block update data transferred thereto fromthe switching means 107 as an intermediate image signal for which thenoise eliminating processing is being executed. Here, the intermediateimage buffer 109 performs a function as an accumulator, and isconstructed so as to hold the results which are obtained by adding a newintermediate image signal to the previously accumulated intermediateimage signal.

Moreover, the control means 112 operates so as to control the readingmeans such as the first input reading means 101, the second inputreading means 102, and the output reading means 104, and the writingmeans such as the intermediate writing means 108, and the output writingmeans 111 to specify a predetermined position and a predetermined sizewhich are used to regulate a predetermined block in the overall image.The predetermined block is specified so that a phase is changed in Kkinds with respect to one block size N.

FIGS. 4A to 4D show block positions in a case where the phase is changedin Embodiment 1 of the present invention. Thus, there are shown theblock positions in the case where the phase is changed in 4 kinds whenK=4. To take a case where one block is set as 8×8 pixels (i.e., N=8) asan example, FIG. 4A shows a state in which no phase is shifted and thusthe blocks are held as they are, which corresponds to the phase K=1.

FIG. 4B shows a state in which the pixels are shifted in a right-handdirection by four pixels and which corresponds to the phase K=2; FIG. 4Cshows a state in which the pixels are shifted in a downward direction byfour pixels and which corresponds to the phase K=3; and FIG. 4D shows astate in which the pixels are shifted in the right-hand direction byfour pixels and in the downward direction by four pixels, and whichcorresponds to the phase K=4.

Here; each of the peripheral blocks of an image does not necessarilyhave a size of N×N pixels. However, with respect to each of thoseportions, the retrieval has only to be carried out for each portionincluding data. Then, the comparing means 105, the retrieving means 106,the switching means 107, and the intermediate writing means 108 operatein the manner described above for the four kinds of phases in accordancewith the operation of the control means 112.

The phase is shifted in such a manner, whereby a plurality ofpredetermined blocks come to overlap one another. As a result, theintermediate image buffer 109 accumulates the updated data for fourtimes (K=4) per pixel. At a time when the accumulation is completed forall the pixels, the multiplying means 110 multiplies the output of theintermediate image buffer 109 by 1/K, thereby carrying out the scaling.As a result, the updated data of each pixel is obtained as an averagevalue for a plurality of phases.

The output after completion of the scaling is written to the outputimage buffer 103 through the output writing means 111 (eleventh line inFIG. 2). The local correlations of the image are detected from multipledirections in such a manner, and the noise is eliminated by utilizingthe direction having the highest correlation. Results of the noiseelimination are written to the output image buffer 103.

When the contents of the intermediate image buffer 109 are transferredto the output image buffer 103, the same processing is repeatedlyexecuted by using the contents of the output image buffer 103 aftercompletion of this update and the contents of the input image buffer 100next time. At this time, the block size is reduced from N×N to N/2×N/2in accordance with the operation of the control means 112, and thenumber of blocks, L, is increased to L×2×2 accordingly (eleventh line inFIG. 2). This is repeated until N becomes Nmin (second line in FIG. 2).A typical value of Nmin is 1.

When a difference between the output image block data read out from theoutput image buffer 103 and the input image block data read out from theinput image buffer 100 is sufficiently small (i.e., when the differenceis equal to or smaller than the predetermined value D), the contents ofthe output image block data read out from the output image buffer 103are outputted from the switching means 107 as they are, and no contentsof the output image buffer 103 are updated.

On the other hand, when the difference between the output image blockdata read out from the output image buffer 103 and the input image blockdata read out from the input image buffer 100 is larger than thepredetermined value D, the contents of the output image buffer 103 areupdated with the retrieval block data which is retrieved as the blockdata having the high correlation by the retrieving means 106.

As described above, the noise eliminating device shown in FIG. 1operates to repeatedly execute the processing for replacing only aportion in which distortion (the difference between the input imagesignal and the output image signal) is large with adjacent data whilethe block size is gradually reduced, thereby eliminating the noisewithout involving large distortion.

Here, the mechanism for eliminating the noise by utilizing this methodis such that the image data for which the replacement is carried outwith a different phase is accumulated in the intermediate image buffer109, and the average value of the image data is calculated by themultiplying means 110.

Considering the fact that the retrieving means 106 outputs the blockcorrelating highly with the predetermined block, it is understood thatthe image signal having the high correlation is preserved, and the noisesignal having the low correlation is attenuated through the averagingprocess. Thus, it can be judged that the noise eliminating device shownin FIG. 1 attenuates only the noise component by utilizing thedifference in local correlations between the image signal and the noisesignal.

As described above, according to Embodiment 1 of the present invention,the local correlations of the image are detected from the multipledirections, and the noise is eliminated by utilizing the directionhaving the highest correlation. Hence, there is an effect in which thenoise is efficiently separated from the image signal as compared withthe prior art, and only the noise component is attenuated.

Note that in Embodiment 1 described above, the two-dimensional stillimage data is used as the input signal. However, the present inventioncan also be applied to a multidimensional signal of a moving image orthe like by increasing the retrieval range for the block in a timedirection.

In addition, in the above description of Embodiment 1, the noiseeliminating device has the function of eliminating the general noise asthe effect of Embodiment 1. However, the noise eliminating device of thepresent invention is not limited to Embodiment 1. Thus, the noise mayalso be a signal which carries information. That is, a technique such asdigital watermarking or steganography is known in which a meaningfulnoise is added to a signal to conceal information. According to thepresent invention, there is offered an effect in which the signal thusembedded is attenuated and the remaining signal is spatially shifted,thereby disturbing detection of the information.

1. A noise eliminating device for eliminating a noise contained in aninput image signal to generate an output image signal, comprising: aninput image buffer for storing the input image signal; an output imagebuffer for storing the output image signal; an intermediate image bufferfor storing an intermediate image signal for which a noise eliminatingprocessing is being executed; a first input reading means for readingout an image signal of a predetermined block specified by apredetermined position and a predetermined size as input image blockdata from the input image buffer; a second input reading means forreading out image signals containing the image signals of thepredetermined block and vicinities of the predetermined block asreference data from the input image buffer; output reading means forreading out an image signal of the predetermined block as output imageblock data from the output image buffer; comparing means for comparing adifference signal representing a difference between the input image datablock and the output image block data with a predetermined value;retrieving means for retrieving block data correlating with the inputimage block data as retrieval block data from the reference data;switching means for receiving as its inputs the output image block dataand the retrieval block data to select the output image block data asoutput image block update data when a level of the difference signal isequal to or smaller than the predetermined value based on comparisonresults obtained by the comparing means and to select the retrievalblock data as output image block update data when the level of thedifference signal is larger than the predetermined value based on thecomparison results obtained by the comparing means; intermediate writingmeans for writing, to the intermediate image buffer, the output imageblock update data selected by the switching means as the intermediateimage signal for which the noise eliminating processing is beingexecuted; multiplying means for scaling the output image block updatedata accumulated in the intermediate image buffer; output writing meansfor writing the output image block update data scaled by the multiplyingmeans to the output image buffer; and control means for carrying outoverall control to successively set a plurality of predetermined blockseach having a predetermined size for a plurality of predeterminedpositions, and to update output image data accumulated in the outputimage buffer with a plurality of output image block update datarespectively corresponding to the plurality of predetermined blocks. 2.A noise eliminating device according to claim 1, wherein the controlmeans sets the plurality of predetermined positions so that theplurality of predetermined blocks overlap one another.
 3. A noiseeliminating device according to claim 1 or 2, wherein the control meanscarries out overall control so that the predetermined size used toregulate a size of a predetermined block when the output image dataaccumulated in the output image buffer is updated is set to graduallyreduce, and the output image signal is repeatedly updated incorrespondence to the size of the predetermined block.
 4. A program fora noise eliminating device that eliminates a noise contained in an inputimage signal to generate an output image signal, wherein the programcauses a computer to execute: a first input reading means for readingout an image signal of a predetermined block specified by apredetermined position and a predetermined size as input image blockdata from an input image buffer for storing the input image signal; asecond input reading means for reading out image signals containing theimage signals of the predetermined block and vicinities of thepredetermined block as reference data from the input image buffer;output reading means for reading out an image signal of thepredetermined block as output image block data from an output imagebuffer for storing the output image signal; comparing means forcomparing a difference signal representing a difference between theinput image data block and the output image block data with apredetermined value; retrieving means for retrieving block datacorrelating with the input image block data as retrieval block data fromthe reference data; switching means for receiving as its inputs theoutput image block data and the retrieval block data to select theoutput image block data as output image block update data when a levelof the difference signal is equal to or smaller than the predeterminedvalue based on comparison results obtained by the comparing means and toselect the retrieval block data as output image block update data whenthe level of the difference signal is larger than the predeterminedvalue based on the comparison results obtained by the comparing means;intermediate writing means for writing, to an intermediate image buffer,the output image block update data selected by the switching means as anintermediate image signal for which a noise eliminating processing isbeing executed; multiplying means for scaling the output image blockupdate data accumulated in the intermediate image buffer; output writingmeans for writing the output image block update data scaled by themultiplying means to the output image buffer; and control means forcarrying out overall control to successively set a plurality ofpredetermined blocks each having a predetermined size for a plurality ofpredetermined positions, and to update output image data accumulated inthe output image buffer with a plurality of output image block updatedata respectively corresponding to the plurality of predeterminedblocks.